Membrane cholesterol alters gallbladder muscle contractility in
prairie dogs.
Yu, Peirong, Qian Chen, Piero Biancani, and Jose Behar.
Department of Medicine, Rhode Island Hospital and Brown University
School of Medicine, Providence, RI 02903
APStracts 3:0027G, 1996.
The cause and effect relationship between membrane cholesterol and
gallbladder muscle contractility was examined by altering membrane
cholesterol to phospholipid mole ratio using cholesterol-rich or
cholesterol-free liposomes. Gallbladder single muscle cells from
prairie dogs fed either a regular diet or high cholesterol (1.2%)
diet were isolated enzymatically with collagenase. Plasma membranes
of gallbladder muscle were purified in sucrose gradient. Cholesterol
was measured using the cholesterol oxidase method. Phospholipids were
measured with the method of Bartlett. Results: 1) after high
cholesterol feeding, cholesterol contents and
cholesterol:phospholipid mole ratio in plasma membranes of
gallbladder muscle increased 90%; muscle cell contraction in response
to CCK-8 decreased 58%; 2) similar changes were observed when normal
gallbladder muscle cells were incubated with cholesterol-rich
liposomes for 2 h; and 3) the changes induced either in vivo or in
vitro were reversed when muscle cells were subsequently incubated
with cholesterol-free liposomes for 2 to 6 hours. We conclude that
gallbladder muscle may incorporate excess cholesterol into its plasma
membrane when exposed to a cholesterol-rich environment; excess
membrane cholesterol impairs muscle contractility; and these changes
appear to be reversible.
Received 28 June 1995; accepted in final form 21 December 1995.
APS Manuscript Number G277-5.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 29 January 96